A whole lot of rain is on the way for Portland and much of the rest of the area this weekend. Rain arrived last night and probably won't stop until late Sunday. A cold front is stalling out over just east of the Cascades. With the front stalled out we're going to see waves of precipitation arrive off the coast.
Our futurecast computer model which is based on the National Weather Services (NWS) North American Model (NAM) is predicting 1.75" To 2.00" of rain by Sunday.
By Sunday the front will sag south, rain in the Cascades will transition to snow. Snow levels by Sunday night will fall well below pass levels. The mountain snow won't last long, drier and colder air will arrive by Tuesday. A big ridge of high pressure will set up in the Rocky Mountain region. The colder dry air will keep storms from reaching the Pacific Northwest.
If you're traveling by road for the Thanksgiving holiday, expect dry but chilly conditions over the mountain passes.